This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A175807 #18 Feb 08 2016 02:47:38
%S A175807 2,3,4,5,12,22,26,154
%N A175807 A007318-perfect numbers.
%C A175807 See definition in comment to A175522. The definition is applied to the flattened view of the binomial coefficients with a single index, without regard to fact that A007318 is a triangle.
%C A175807 No more terms up to 10^6. - _Michel Marcus_, Feb 07 2016
%e A175807 Since A007318(1)+ A007318(2)+ A007318(3)+ A007318(4)+ A007318(6)=6= A007318(12), then 12 is in the sequence.
%p A175807 A007318 := proc(n) option remember; local t,r; t := 0 ; for r from 0 do if t+r+1 > n then return binomial(r,n-t) ; end if; t := t+r+1 ; end do: end proc:
%p A175807 isA175807 := proc(n) m := 0 ; for d in numtheory[divisors](n) minus {n} do m := m+A007318(d) ; end do; m = A007318(n) ; end proc:
%p A175807 for n from 1 do if isA175807(n) then printf("%d,\n",n); end if; end do: # _R. J. Mathar_, Dec 05 2010
%o A175807 (PARI) b(n) = {my(m = 1); while (m*(m+1)/2 < n, m++); if (! ispolygonal(n, 3), m--); binomial(m, n - m*(m+1)/2);}
%o A175807 isok(n) = sumdiv(n, d, (d<n)* b(d)) == b(n); \\ _Michel Marcus_, Feb 07 2016
%Y A175807 Cf. A175811, A175522, A000396.
%K A175807 nonn,less,more
%O A175807 1,1
%A A175807 _Vladimir Shevelev_, Dec 05 2010